Characteristics of light, such as Raman scattering, spontaneous glow, plasma incandescence, fluorescence, phosphorescence, and synchrotron radiation, etc., which occur due to the laws of physics, chemistry, or plasma reactions (hereafter, these reactions are referred to as, “reaction”), greatly depend on the minute mechanism of light emission and on changes in these reactions. Therefore, the characteristics of the reaction and its correlation with the reactive amounts can be determined by measuring the light resulting from such a minute mechanism. Moreover, it is possible to control the reaction based on information obtained from the measurement of a minute reaction mechanism, and information on the rate of change of the reaction can be determined from measurements made with high time resolution. Moreover, it is possible to obtain useful data to improve the device that generates the reaction. Such a measurement is necessary to control and improve various types of combustion equipment by analyzing combustion in an automobile engine, gas turbine, etc.
To determine the minute mechanism of the above-mentioned reaction from spectral measurements, it is necessary to obtain a “local” measurement, that is, a measurement in a small volume, relative to the space in which the reaction occurs. It is also necessary to acquire time-series measurements, that is, measurements that are repeatedly and continuously made in short time intervals, relative to the time interval over which the reaction mechanism changes.
In non-patent document 1, an optical measurement device that measures the spontaneous glow, or natural luminescence, of the reaction has been described; this device is capable of achieving the measurements described above. This optical measurement device has achieved local, real-time measurements of the reaction by means of focusing optics and a catoptric system designed for local point measurements, by reducing the volume in which the measurement is made to 1.6 mm×φ0.2 mm, and by sampling at a high rate of 250 kHz using a photoelectric tube as the light-receiving means combined with high-speed processing. Moreover, in this document, the device is described as an instrument used to measure the spontaneous glow of the reaction by simultaneously measuring each wavelength corresponding to the luminescence from the three chemical species OH*, CH*, and C2*.
Additionally, as already described in patent document 1, the inventors are proposing an optical measurement device, which can efficiently make local, high-resolution, time-series measurements of light from two or more measurement points. This optical measurement device measures the luminescence of the combustion reaction within the local part of the combustion chamber, using a catoptric system, and detects the local reactive characteristics.
In this optical measurement device, the light emitted from the reaction in the local part or the combustion chamber, that is an object point of this catoptric system, is measured by arranging the incident edge surface of an optical fiber at the focus position of the catoptric system and by measuring the spectrum of the light that is transported by this optical fiber. Because the surface that contributes to the image formation is a reflective surface in the catoptric system, chromatism does not occur, and, therefore, an accurate measurement of the light, from the reaction can be made.    [Patent Literature 1] Japanese Patent Laid-Open No. 2000-111398    [Non Patent Literature 1] Proceedings of the Thirty-Fifth Japanese Symposium on Combustion, p. 54-56 (1997)
The spectroscope used in the above-mentioned optical measurement device evenly measures the light from the measurement point across all wavelengths of the optical spectrum. In other words, the device measures the light at wavelengths beyond those necessary to obtain information on a minute mechanism of the reaction. Therefore, for efficient analysis of only relevant portions of the spectrum, it is necessary to disregard the light at non-relevant wavelengths. As a result, the resolution of specific wavelengths of light in relevant emission bands might be insufficient in an optical measurement device with such a catoptric system. Moreover, the spectroscope may become large and unwieldy if adequate wavelength resolution is secured for all wavelengths. Thus, it is comparatively difficult to manufacture or use such a spectroscope that has adequate performance.
The present invention is proposed to solve these problems. Provided is a spectroscope that can be manufactured easily and can provide high wavelength resolution within a specific spectral band.